Metallic filament incandescent electric lamp and the manufacture thereof



Nov. 29, 1949 R. K. BRAUNSDORFF 2,439,261

I METALLIC FILAMENT INCANDESCENT ELECTRIC LAMP AND THE MANUFACTURE THEREOF Original Filed Feb. 29, 1944 INVENTOR ifs/mm /f5FAl/A/$00AFF M WY m:

ATTO ME Patented Nov. 29, 1949 METALLIC FILAMENT INCANDESCENT ELEC- TRIO LAMP AND THE MANUFACTURE THEREOF Reginald K. Braunsdorff, East Orange, N. J., as-

signor to Tung-Sol Lamp Works, Inc., Newark, N. J., a corporation of Delaware Continuation of application Serial No. 524,385, February 29, 1944. This application April 15, 1948, Serial No. 21,276

11 Claims. 1

This invention relates to tungsten incandescent lamps and the manufacture thereof.

It is known that zirconium in the form of a powder, paste or the like is useful in evacuated envelopes used for incandescent lamps as a getter for absorbing residual gases remaining after evacnation of the envelope or evolved durin the operation of the electric device. In my application Serial No. 480,438, filed March 25, 1943, abandoned October 11, 1945; and application Serial No. 621,047 filed October 8, 1945, Patent No. 2,444,423 issued July 6, 1948; and application Serial No. 621,046 filed October 8, 1945, Patent No. 2,462,837 issued March 1, 1949, I have set forth the use of solid zirconium metal as a getter material in several forms.

I have now found that the getter action may be substantially improved by volatizing zirconium in the sealed envelope by burning out or flashing a metallic wire of zirconium connected across the terminals of the tungsten filament and disposed in the vicinity of the filament. The momentary arc resulting from the flash apparently combines the residual oxygen and nitrogen which may be present with the zirconium and the zirconium metal apparently has the property of absorbing its own oxides and nitrides into molten or metallic form, thereby offering new metallic surfaces for further getter action. The getter action produced by the flash of the zirconium metal is so pronounced in some cases as to render less important the obtaining of the usual high vacuum prior to seal off. For example, envelopes cleaned up in this fashion having original air content at atmospheric pressure would later on high voltage ionization test, show satisfactory degree of exhaust, indicating combination of the zirconium with the oxygen and nitrogen present in the atmosphere sufficient to avoid the necessity of the usual evacuating or high evacuating step.

One object of the invention therefore is the volatilizing or flashing of zirconium metal in the manufacture of the incandescent lamp as below set forth.

A further object of the invention is the utilization of two distinct phases in the getter action by the use of zirconium metal, one phase being the initial flash to combine the gases in the are or vaporization condition of zirconium followed by the second phase or prolonged getter action from the residue material remaining after the flash of the zirconium within the intense heat range of the filament.

For a better understanding of the invention reference may be had to the accompanying drawings wherein Figs. 1, 2 and 3 illustrate steps in the manufacture of a miniature incandescent lamp according to the invention; and

Fig. 4 shows a slightly modified form of filament mount.

Referring to the drawings, I have chosen for illustrating the invention the application thereof to miniature incandescent lamps. Figs. 1, 2 and 3 show three diiferent steps in the manufacture. The lamp embodies the conventional envelope l containing a conventional press 2. Mounted in the press 2 are two conventional support wires 3 carrying a conventional filament 4 as, for example, the major filament of a double filament headlight lamp. The support wires 3 project up above the filament 4 and across the ends 3' is fastened a wire 5 of zirconium. Fig. 2 illustrates the connection of the leads 6 to an electric supply circuit 1 with a source of direct current 8 supplying the circuit 1, such for example as a battery. A switch 9 is shown in the circuit 1 for connectin and disconnecting the leads 6 across the supply circuit. At i0 is shown a conventional resistance in one side of the circuit 1 for controlling the voltage applied to the filament 4 and the zirconium wire 5. Fig. 3 illustrates a third step in the manufacture of the incandescent lamp wherein the zirconium wire is burned out or flashed out and caused to be balled back into solid getter material 5 on the support wires.

The connection of the zirconium wire across the leads of the filament provides a simple: and inexpensive way of practicing the zirconium flashing step in the manufacture. The zirconium wire may be burned or flashed out before the filament 4 reaches an oxidizing temperature but this has 7 the disadvantage among others, that the zirconium flash would be expected to absorb by almost instantaneous arc condition the gas residue and therefore that getter action is expected in too short a period of time and the further disadvantage that the flash would tend to volatilize and splash metallic vapor over on the comparatively cold tungsten filament which is not desirable because of its tendency to combine to form zirconium tungstate. An alternative is to choose the zirconium wire of a size and length such that both the zirconium section 5 and the filament 4 are simultaneously brought up to a lighted condition. The lighting of the lamp filament in itself will prevent deposit of any zirconium vapor metal on the filament surface. By choosing the correct diameter of the zirconium wire it can be arranged that the zirconium wire will fail, that is, flash or burn out at a current value under that of the filament wire i. This provides two sources of heat for driving out residual gases from the leads and these gases are slowly combined or absorbedfduring the period of lightup. Even with the-presence of air in the bulb, the zirconium flash or are appears to absorb the same prior to any appreciable oxidation of the filament i. Thisis a" func- 4 By the use of this method in the manufacture of the incandescent lamp bulbs it is unimportant whether high vacuums are initially obtained by the usual evacuating apparatus since the zir- 5 COIIiLImJ flQIShIDIeaIC appears vto'idispose of any air-which istrapped inside the sealed bulb or .tube. For example, an incandescent lamp, though not initially evacuated, was in efiect eevacuatedrbyixtherflashing or arcing of the zirtion of wire size and may becarefully.controlledil0iconiumawire inside the bulb, and the lamp even during mounting. This method of lamp manufacture where the zirconiumwire is flashed prior to or after the filament i reaches an oxidizing temperature contributes toward a higherv lamp quality. A pro-oxidation of secondary metal in the bulb is obtained and residual atmospheric air is cleaned up, preparing the lamp for the regular burning of the main filament throughout the normal life of the lamp. Moreover, there -is.ino evidence of deposit on the bulb walls and the arcing..and volatization .of the. .zirconium :does -,not produce any silvering action. Zirconium'hasxa relatively; high .melting. point, namely above, that ofthenickel IeadsFS-butunder thatoi the tungsten filament and as..above;-pointed out, the zirconium. functions. in the--manner=indicatedz to produce the highly useful results obtained. :The solid-zirconium, remaining at the ends of the wire 5.,after flashing and .the-solid materialresulting from-the flashing ofz the wire and the combination ofntherresiduali gases 'with'the volatilized zirconium. remainaftentheiiash as protuberanceszor balls-,5 to; carry ,onthe getter action duringithe normal liferoiothalamp. .It is observed that the solid.,zirconium and zirconium: alloy material: v5' are inv close yicinity'. to thee-heated filament. izand therefore inthehottestipart of-t'he-Joulb WhiChiiS the ..most -,-satisfactory relationship existing 1' for continued-satisfactory getter action.

In Fig. Axis illustrated ,avslightly diiierentwform ofriilament..-and mountswherein theeu-pper ends 3 .-.of1. the nickel lead :wires 3 are turned; inwardly towardseachother-and the :filament i is mounted above; the. inwardly. turned ends 53' ;.of"the:*wires. The zirconium-wire. 5 ,i-nx,this:case,=.asshown in dotted-lines, isoriginally connected-directly.across theinwa-rdly turned-end lead tips 3. This provides the shortest practical length i for convenience and 'IOWwCOSt :of wire :and also positions the wire inzthes-most favorableeposition' to secure the furtheuggetter-action. it also minimizes the'voltage required to are out this zbrid'ging orshort circuiting zirconium-wire li to obtain the: solid residualggetter material: 5. In: both the modifications wire connected directly across the tip-ends oithe leadrwi-resbut it is understood that the zirconium wire :may-be caused .to' assume any suitable -shape ask-for example, a 'smalliU shape was to avoid interferenceat welding.

illmavembtained particularly good results by so choosing. the zirconium wire 5 with respectto the filamentffl as to-cause the lighting of the filament 4-;iprior..to the burnout or flashing ofthe zirconium. :-For: example, with the iull'filament-voltage. oft-volts I have provided a zirconium wire 5 which. flashedout at around about 4 volts, at which-voltage the filament l was burning *dimly atthe time theburn or flash out occurred. Therez was no damage to the filament l during the time that the zirconium wire was incandescent an'd'the voltage went'up to the normal 6 volts as determinedby the supply circuit '5 and the resistance regulator ill.

with no initialevacuation gives satisfactory re- .sults. .By..the .use .of the invention imperfect eeua-cuations. arerendered harmless and it is not essential-Ito obtain;:high vacuums.

5 This invention may be applied to other types ot-bulbs ofthegasfilled or evacuated type whereiinia high chemical; purity is desired. It is also applicable to electric bulbs having various types ofsimetallic supporting leads and electrodes, as for instance, leads of nickel or platinum sheathed leads. By. introducinga .pieceoi. zirconium v.wire in or about-.thaoperative'pr.heated .po'rtioniof the.b.ulb.=and.-. across .the. terminals ,thereof, ,;the flashingwoperation will .cause partof the zirconium wire .to..provide.- the glitter action, while the. remaininsparts of the zirconium ..wire will ball back .on...the..leads.to, which they are.attached. Since these zirconium parts or'balls remain .in thevicinity of the. operative portion of-.the .bulb, they. act as .a sponge .to .absorb residualgases Lthat..might destroy .the .chemical purity .within the .bulb. .By using. zirconium wire of..the .ordenof 'fivethousandths of an inch. thick, it is possible, .to obtain zirconium. globules or. balls ranging from. .(llOto .015 inch on, theelectrodes. The'degree of getter action obtained byjflashing zirconium wire inan evacuated'orgas-filled bulb wherein. the remaining portions. of the zirconium remain in the vicinity of the. operative part of-the bulb, is quite pronounced. For example, .startingwithan atmosphere of air in theitube suflicient, getter. action was obtained to-rnaintain a clear-bulb duringltheburnout period "and with ame'duceddegree of .burning intensity adequate getter action'may be obtained throughout the entire life performance of "the tube. On' the assumption that air contentis 80%-nitrogen and 20% 'oxygenyl found that t-he zirconium would meet and sustain this 0 gasicondition without: providing excessive oxidation :orblackening. Asabove pointed outythe zirconiumsmetal has-the property of 2 absorbing its owmnitridesiandoxides into-molten or metallic formtherebyeoiferingr new metallic-surfacesrfor v r3! further .getter actionandtubescleanedupin I chavegshownr the zirconium wire as a a straight thisiashion having original ia-irwcontent atwatmospheric pressure would latertest satisfactory indicating the eelimina-tion of the oxygen and nitrogen .present in theatmosphere :by' combination wwith the :flashi-ng :volatil-iZed -zirconium. Tubes made in. this manner-:have a satisfactory degree. of..exhaust.

The. initial flashing of the rzi-rconium igetter wireas .above set forth: results .inan initial cleanup of oxide residue, forming stable oxides of zirconium which .in-the final aformis non-reaotive. Dependent. on .the amount-of oxide present-zir coniumoxide will be formed tothe-degree. otfirst combustion .and..,thrown oif. immediately onathe glass walls of the=.bu1b .or: envelope. :as a .stable oxide. Asialzirconiumoxide it will beless blackening than normal..discolorationof the envelope due .to the burning-pf .the tungsten-filament.- This/invention has the further.iadva-ntage.of 1 75. leaving asubstantial .quantity. of ,unconsumod structure.

or excess zirconium metal attached to the leads near the tungsten filament, namely in a high temperature zone which will continue to provide gettering action. By being so disposed on the supporting leads by the flashing operation at a point where the temperature of the zirconium reaches a minimum of 400 C. and above, we accomplish absorption of residual gases slowly given off by the leads. C0, C02 and H2 and other gases are probably present within the nickel With the continued burning of the tungsten filament and associated heating of leads these gases are slowly given ofi to contaminate either the vacuum or argon-filled atmosphere that is intentionally introduced into the lamp bulb. Since it is desired to retain the high chemical purity of the argon gas alone, it is important to absorb any residual gases that may destroy this purity of atmosphere. Forming zirconium oxide results in a stable salt, while the excess of zirconium metal acts as a sponge to take up residual gases. The invention can be practiced in a manner to provide suflicient excess zirconium on the leads in the hot zone to last the entire life of the tungsten filament. In order to get adequate functioning it is necessary to mount the zirconium structure or wire which is flashed in the high temperature zone where the excess or balled up zirconium is subject to continued heating.

The invention has marked utility in evacuated envelopes wherein the getter wire and deposit may be melted in a hot zone which is subjected to a temperature high enough to cause the getter to act as a sponge in the absorption of the deleterious gases evolved during the normal life of the envelope with the flashing out of the filament wire also taking place in the high temperature zone.

By lighting the filament and the getter wire together and then flashing out the getter wire, the metallic vapor produced by the flashing out process is not deposited on the filament.

While I prefer zirconium as the getter of which the wire is made, the invention has some utility with other getter metals and particularly metals from the same family as zirconium such, for example, as tantalum.

This application is a continuation of my application Serial No. 524,385, filed February 29, 1944, abandoned April 17, 1948.

I claim:

1. The method of gettering an incandescent lamp having a metallic filament comprising the steps of mounting a getter wire in close proximity to the filament for electrical energization, energizing and lighting and flashing out the getter wire and preventing the deposition of vaporized getter wire on the filament during the flashing out by simultaneously lighting the filament and the getter wire.

2. The method of gettering an incandescent lamp having an unshielded metallic filament comprising the step of mounting a getter wire in close proximity to the filament for electrical energization, energizing and lighting and flashing out the getter wire and preventing the deposition of vaporized getter wire on the filament during the flashing out by simultaneously lighting the filament and the getter wire.

3. The method of gettering a metallic filament incandescent lamp comprising connecting a wire of a gettering material across the filament terminals in the lamp and in close proximity to the filament, passing an electric current through the filament and zirconium to bring them to a lighted condition andthen burn out the wire to getter the lamp, said lighting of the filament and zirconium prior to the burning out of the latter preventing the deposition of getter material on the filament.

, 4. The method of gettering an incandescent lamp havin a metallic filament comprising the steps of mounting a zirconium getter wire in close proximity to the filament for electrical energization, energizing and lighting and flashing out the getter wire and preventing the deposition oi vaporized getter wire on the filament during the flashing out by simultaneously lightin the filament and the getter wire.

5. The method of gettering a'metallic filament incandescent lamp comprising connecting a getter wire of zirconium across the filament terminals in the lamp and in close proximity to the filament, passing an electric current through the filament and zirconium to bring them to a lighted condition and then burn out the wire to getter the lamp, said lighting of the filament and zirconium prior to the burning out of the latter preventing the deposition of getter material on the filament.

6. The method of gettering a metallic filament incandescent electric lamp which comprises the steps of connecting a wire of a getter metal directly across the terminals of the filament and at points closely adjacent the filament and then passing suflicient current through the getter wire to burn out and flash the same with the ends of the getter wire balling up at the filament terminals to leave thereon a gettering material which continues its gettering function during the normal life of the lamp.

7. The method of making and gettering an incandescent lamp which comprises the steps of connecting a wire of zirconium and the like across the terminals of the lamp immediately adjacent to the filament and burning out and flashing said zirconium wire, said wire being volatilized while the filament of the lamp is heated to a temperature below the oxidizing temperature.

8. The method of making and gettering an incandescent lamp which comprises the steps of connecting a wire of zirconium and the like across the terminals of the lamp and burning out and flashing said zirconium wire, the filament of said lamp glowing at the time the zirconium wire is burned out whereby part of said zirconium combines with the oxygen residue to initially clean up the lamp by forming stable oxides of zirconium and the remainder of said zirconium attached to the terminals of the lamp and subjected to a minimum temperature of 400 C. operates to absorb residual gases contaminating the atmosphere during the life of the lamp.

9. The method of making and gettering an incandescent lamp which comprises the steps of connecting a wire of zirconium and the like across the terminals of the lamp and burning out and flashing said zirconium wire, said zirconium wire upon being burned out balling up upon the terminals to leave a continuing gettering material.

10. The method of making and gettering an incandescent lamp which comprises the steps of connecting a wire of zirconium and the like directly across the terminals of the lamp for energizing the filament and burning out and flashing said zirconium wire, said zirconium wire being closely positioned to the filament of the lampzandupon bfirmngzliout balling-up: at the terminals"tohleaveithereonea continuing gettering: material tozcontinuouslyzabsorbcontaminating :gases given dfi'zibysthewmetallic:members in the lamp duringzthel lifeaf -the lamp, and said flashed portion of the zirconium wirercombining withthesremainingzloxygen in the lamp' -to form stable:zirconiumsoxides.

1 1 The:;meth(1dloifrmaking a sealed envelope having :electricxtenminaslsitherein and; a filament 1 across said terminals :whichscomprises r the steps ofzrconnecting=.acr0ss:;:said ttermi'nals at a point adjacent the filament".a wires'containing a getter materiakandtfla'shing"andiburning out said wire .REFERENCES CITED iThefollowing references are'of record in the file of" this patent:

5 UNITED STATES PATENTS Number "Name Date 3,394,396 Mouromtsefi et a1. Feb.5, 1946 O FOREIGN PATENTS Number Country Date 5365 Norway Mar.:3, 1897 520 835 .Great Britain May 6,1940

while the fi1ament:. -is :heatedt;@t0 aupoint-below 15 themormal: operatingiatemperature.

JREGINALDiK-L BRAUNSDORFF. 

